Hydrocarbon dehydrogenation with a multimetallic catalytic composite

ABSTRACT

Dehydrogenatable hydrocarbons are dehydrogenated by contacting them at hydrocarbon dehydrogenation conditions with a multimetallic catalytic composite comprising a combination of a catalytically effective amount of a pyrolyzed ruthenium carbonyl component with a porous carrier material containing a uniform dispersion of catalytically effective amounts of a platinum group component maintained in the elemental metallic state, and of a rhenium component. An optional non-acidic multimetallic catalytic composite disclosed herein is a combination of a catalytically effective amount of a pyrolyzed ruthenium carbonyl component with a porous carrier material containing a uniform dispersion of catalytically effective amounts of a platinum group component which is maintained in the elemental metallic state during the incorporation of the ruthenium carbonyl component, a rhenium component, and an alkali or alkaline earth component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of my prior, copending application Ser.No. 301,065 filed Sept. 11, 1981 (assigned U.S. Pat. No. 4,369,540)which is a continuation-in-part of my prior application Ser. No. 246,828filed Mar. 23, 1981, now U.S. Pat. No. 4,358,399, which in turn is adivision of my prior application Ser. No. 82,436 filed Oct. 5, 1971 andissued May 19, 1981 as U.S. Pat. No. 4,268,377, which in turn is acontinuation-in-part of my prior application Ser. No. 848,699 filed Nov.4, 1977 and issued Jan. 15, 1980 as U.S. Pat. No. 4,183,804. All of theteachings of these applications are specifically incorporated herein byreference.

BRIEF SUMMARY OF THE INVENTION

The subject of the present invention is, broadly, an improved method fordehydrogenating a dehydrogenatable hydrocarbon to produce a hydrocarbonproduct containing the same number of carbon atoms but fewer hydrogenatoms. In another aspect, the present invention involves a method ofdehydrogenating normal paraffin hydrocarbons containing 3 to 30 carbonatoms per molecule to the corresponding normal mono-olefin with minimumproduction of side products. In yet another aspect, the presentinvention relates to a multimetallic catalytic composite comprising acombination of a catalytically effective amount of a pyrolyzed rutheniumcarbonyl component with a porous carrier material containing a uniformdispersion of catalytically effective amounts of platinum groupcomponent which is maintained in the elemental metallic state, and arhenium component. This composite has highly beneficial characteristicsof activity, selectivity, and stability when it is employed in thedehydrogenation of dehydrogenatable hydrocarbons such as aliphatichydrocarbons, naphthene hydrocarbons, and alkylaromatic hydrocarbons.

DETAILED DESCRIPTION

The conception of the present invention followed from my search for anovel catalytic composite possessing a hydrogenation-dehydrogenationfunction, a controllable cracking function, and superior conversion,selectivity, and stability characteristics when employed in hydrocarbonconversion processes that have traditionally utilized dualfunctioncatalytic composites. In my prior application Ser. No. 246,828, Idisclosed a significant finding with respect to a multimetalliccatalytic composite meeting these requirements. More specifically, Idetermined that a pyrolyzed ruthenium carbonyl component can beutilized, under certain specified conditions, to beneficially interactwith the platinum group and rhenium components of a dual-functioncatalyst with a resulting marked improvement in the performance of sucha catalyst. Now I have ascertained that a catalytic composite,comprising a combination of catalytically effective amounts of apyrolyzed ruthenium carbonyl component, a platinum group component and arhenium component with a porous carrier material can have superioractivity, selectivity and stability characterisitics when it is employedin a hydrocarbon dehydrogenation process if these components areuniformly dispersed in the porous carrier material in the amountsspecified hereinafter and if the oxidation state of the platinum groupcomponent is carefully controlled so that substantially all of thiscomponent is present in the elemental metallic state during theincorporation of the ruthenium carbonyl component. I have discerned,moreover, that a particularly preferred multimetallic catalyticcomposite of this type contains not only a pyrolyzed ruthenium carbonylcomponent, a platinum group component, and a rhenium component, but alsoan alkali or alkaline earth component in an amount sufficient to ensurethat the resulting catalyst is nonacidic.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products, such as detergents, plastics, synthetic rubbers,pharmaceutical products, high otane gasolines, perfumes, drying oils,ion-exchange resins, and various other products well known to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C₃ and C₄ mono-olefins to alkylateisobutane. Another example of this demand is in the dehydrogenation ofnormal paraffin hydrocarbons to produce normal mono-olefins having 3 to30 carbon atoms per molecule. These normal mono-olefins can, in turn, beutilized in the synthesis of a vast number of other chemical products.For example, derivatives of normal mono-olefins have become ofsubstantial importance to the detergent industry where they are utilizedto alkylate an aromatic, such as benzene, with subsequent transformationof the product arylalkane into a wide variety of biodegradabledetergents such as alkylaryl sulfonate types of detergents which aremost widely used today for household, industrial, and commercialpurposes. Still another large class of detergents produced from thesenormal mono-olefins are the oxyalkylated phenol derivatives in which thealkylphenol base is prepared by the alkylation of phenol with thesenormal mono-olefins. Still another type of detergent produced from thesenormal mono-olelfins are the biodegradable alkylsulfonates formed by thedirect sulfation of the normal mono-olefins. Likewise, the olefin can besubjected to direct sulfonation with sodium bisulfite to makebiodegradable alkylsulfonates. As a further example, these mono-olefinscan be hydrated to produce alcohols which then, in turn, can be used toproduce plasticizers and/or synthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, they find wide application in the petroleum,petrochemical, pharmaceutical, detergent, plastic, and the likeindustries. For example, ethylbenzene is dehydrogenated to producestyrene which is utilized in the manufacture of polystyrene plastics,styrene-butadiene rubber, and the like products. Isopropylbenzene isdehydrogenated to form alpha-methyl styrene which, in turn, isextensively used in polymer formation and in the manufacture of dryingoils, ion-exchange resins, and the like materials.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of a dehydrogenatable hydrocarbon bycontacting the hydrocarbon with a suitable catalyst at dehydrogenationconditions. As is the case with most catalytic procedures, the principalmeasure of effectiveness for this dehydrogenation method involves theability of the catalyst to perform its intended function with minimuminterference of side reactions for extended periods of time. Theanalytical terms used in the art to broadly measure how well aparticular catalyst performs its intended functions in a particularhydrocarbon conversion reaction are activity, selectivity, andstability, and for purposes of discussion here, these terms aregenerally defined for a given reactant as follows: (1) activity is ameasure of the catalyst's ability to convert the hydrocarbon reactantinto products at a specified severity level where severity level meansthe specific reaction conditions used--that is, the temperature,pressure, contact time, and presence of diluents such as H₂ ; (2)selectivity usually refers to the amount of desired product or productsobtained relative to the amount of the reactant charged or converted;(3) stability refers to the rate of change with time of the activity andselectivity parameters--obviously, the smaller rate implying the morestable catalyst. In a dehydrogenation process, more specifically,activity commonly refers to the amount of conversion that takes placefor a given dehydrogenatable hydrocarbon at a specified severity leveland is typically measured on the basis of disappearance of thedehydrogenatable hydrocarbon; selectivity is typically measured by theamount, calculated on a mole or weight percent of converteddehydrogenatable hydrocarbon basis, of the desired dehydrogenatedhydrocarbon obtained at the particular activity or severity level; andstability is typically equated to the rate of change with time ofactivity as measured by disapparance of the dehydrogenatable hydrocarbonand of selectivity as measured by the amount of desired dehydrogenatedhydrocarbon produced. Accordingly, the major problem facing workers inthe hydrocarbon dehydrogenation art is the development of a more activeand selective catalytic composite that has good stabilitycharacteristics.

I have now found a multimetallic catalytic composite which possessesimproved activity, selectivity, and stability when it is employed in aprocess for the dehydrogenation of dehydrogenatable hydrocarbons. Inparticular, I have determined that the use of a multimetallic catalyst,comprising a combination of catalyticaly effective amounts of apyrolyzed ruthnium carbonyl component, a platinum group component, and arhenium component with a porous carrier material, can enable theperformance of a hydrocarbon dehydrogenation process to be substantiallyimproved if the platinum group component is uniformly dispersedthroughout the carrier material prior to incorporation of the rutheniumcarbonyl component, if the oxidation state of the platinum groupcomponent is maintained in the elemental metallic state prior to andduring contact with the ruthenium carbonyl component and if hightemperature treatments in the presence of oxygen and/or water of thereaction product of the ruthenium carbonyl component with the carriermaterial containing the platinum group component is avoided. Moreover,particularly good results are obtained when this composite is combinedwith an amount of an alkali or alkaline earth component sufficient toensure that the resulting catalyst is nonacidic and utilized to producedehydrogenated hydrocarbons containing the same carbon structure as thereactant hydrocarbon but fewer hydrogen atoms. This nonacidic compositeis particularly useful in the dehydrogenation of long chain normalparaffins to produce the corresponding normal mono-olefin withminimization of side reactions such as skeletal isomerization,aromatization, cracking and polyolefin formation. In sum, the presentinvention involes the significant finding that a pyrolyzed rutheniumcarbonyl component can be utilized under the circumstances specifiedherein to beneficially interact with and promote a hydrocarbondehydrogenation catalyst containing a platinum group metal and rhenium.

It is accordingly, one object of the present invention to provide anovel method for the dehydrogenation of dehydrogenatable hydrocarbonsutilizing a multimetallic catalytic composite comprising catalyticallyeffective amounts of a pyrolyzed ruthenium carbonyl component, aplatinum group component, and a rhenium component combined with a porouscarrier material. A second object is to provide a catalytic compositehaving superior performance characteristics when utilized in ahydrocarbon dehydrogenation process. Another object is to provide animproved method for the dehydrogenation of normal paraffin hydrocarbonsto produce normal mono-olefins, which method minimizes undesirablereactions such as cracking, skeletal isomerization, poly-olefinformation, disproportionation and aromatization.

In brief summary, one embodiment of the present invention involes amethod for dehydrogenating a dehydrogenatable hydrocarbon whichcomprises contacting the hydrocarbon at hydrocarbon dehydrogenationconditions with a multimetallic catalytic composite comprising a porouscarrier material containing a uniform dispersion of catalyticallyeffective and available amounts of a pyrolyzed ruthenium carbonylcomponent, a platinum group component, and a rhenium component.Substantially all of the platinum group component is, moreover, presentin the composite in the elemental metallic state during theincorporation of the ruthenium carbonyl component and the pyrolysis ofthe ruthenium carbonyl component is performed after it has been reactedwith the porous carrier material containing the platinum group andrhenium components. Further, these components are preferably present inthis composite in amounts, calculated on an elemental basis, sufficientto result in the composite containing about 0.01 to about 2 wt. %ruthenium derived from the ruthenium carbonyl component, about 0.01 toabout 2 wt. % platinum group metal, and about 0.01 to about 5 wt. %rhenium, and this composite is preferably maintained in a substantiallyhalogne-free state during use in the dehydrogenation method.

A second embodiment relates to the dehydrogenation method described inthe first embodiment wherein the dehydrogenatable hydrocarbon is analiphatic compound containing 2 to 30 carbon atoms per molecule.

A third embodiment comprehends a nonacidic catalytic compositecomprising a porous carrier material having uniformly dispersed thereincatalytically effective and available amounts of a pyrolyzed rutheniumcarbonyl component, a platinum group component, a rhenium component, andan alkali or alkaline earth component. These components are preferablypresent in amounts sufficient to result in the catalytic compositecontaining, on an elemental basis, about 0.01 to about 2 wt. % rutheniumderived from the ruthenium carbonyl component, about 0.01 to about 2 wt.% platinum group metal, about 0.01 to about 5 wt. % rhenium, and about0.1 to about 5 wt. % alkali metal or alkaline earth metal. In addition,substantially all of the platinum group component is present in theelemental metallic state during incorporation of the ruthenium carbonylcomponent, the pyrolysis of the ruthenium carbonyl component occursafter incorporation thereof with the porous carrier material containingthe platinum group and rhenium components, and substantially all of thealkali or alkaline earth component is present in an oxidation stateabove that of the elemental metal.

Another embodiment pertains to a method for dehydrogenating adehydrogenatable hydrocarbon which comprises contacting the hydrocarbonwith the nonacidic catalytic composite described in the third embodimentat dehydrogenation conditions.

Other objects and embodiments of the present invention invole specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of ingredients, suitable methods of multimetalliccomposite preparation, suitable dehydrogenatable hydrocarbons, operatingconditions for use in the dehydrogenation process, and the likeparticulars. These are hereinafter given in the following detaileddiscussion of each of these facets of the present invention. It is to beunderstood that (1) the term "nonacidic" means that the catalystproduces less than 10% conversion of 1-butene to isobutylene when testedat dehydrogenation conditions and, preferably, less than 1%; (2) theexpression "uniformly dispersed throughout the carrier material" isintended to mean that the amount of the subject component, expressed ona weight percent basis, is approximately the same in any reasonablydivisible portion of the carrier material as it is in gross; and (3) theterm "substantially halogen-free" means that the total amount of halogenpresent in the catalytic composite in any form is less than about 0.2wt. %, calculated on an elemental basis.

Regarding the dehydrogenatable hydrocarbon that is subjected to themethod of the present invention, it can, in general, be an oganiccompound having 2 to 30 carbon atoms per molecule and containing at lastone pair of adjacent carbon atoms having hydrogen attached thereto. Thatis, it is intended to include within the scope of the present invention,the dehydrogenation of any organic compound capable of beingdehydrogenated to produce products containing the same number of carbonatoms but fewer hydrogen atoms, and capable of being vaporized at thedehydrogenation temperatures used herein. More particularly, suitabledehydrogenatable hydrocarbons are: aliphatic hydrocarbons containing 2to 30 carbon atoms per molecule, alkylaromatic hydrocarbons where thealkyl group contains 2 to 6 carbon atoms, and naphthenes oralkyl-substituted naphthenes. Specific examples of suitabledehydrogenatable hydrocarbons are: (1) alkanes such as ethane, propane,n-butane, isobutane, n-pentane, isopentane, n-hexane, 2-methylpentane,3-methylpentane, 2,2-dimethylbutane, n-heptane, 2-methylhexane,2,2,3-trimethylbutane, and the like compounds; (2) naphthenes such ascyclopentane, cyclohexane, methylcyclopentane, ethylcyclopentane,n-propylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds;and (3) alkylaromatics such as ethylbenzene, n-butylbenzene,1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene,ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 3 to 30 carbon atoms per molecule. Forexample, normal paraffin hydrocarbons containing about 10 to 18 carbonatoms per molecule are dehydrogenated by the subject method to producethe corresponding normal mono-olefin which can, in turn, be alkylatedwith benzene and sulfonated to make alkylbenzene sulfonate detergentshaving superior biodegradability. Likewise, n-alkanes have 10 to 18carbon atoms per molecule can be dehydrogenated to the correspondingnormal mono-olefin which, in turn, can be sulfonated or sulfated to makeexcellent detergents. Similarly, n-alkanes having 6 to 10 carbon atomscan be dehydrogenated to form the corresponding mono-olefin which can,in turn, be hydrated to produce valuable alcohols. Preferred feedstreams for the manufacture of detergent intermediates contain a mixtureof 4 to 5 adjacent normal paraffin homologues such as C₁₀ to C₁₃, C₁₁ toC₁₄, C₁₁ to C₁₅ and the like mixtures. In an especialy preferredembodiment, the charge stock to the present method is substantially purepropane.

The multimetallic catalyst used in the present invention comprises aporous carrier material or support having combined therewith a uniformdispersion of catalytically effective amounts of a pyrolyzed rutheniumcarbonyl component, a platinum group component, a rhenium component,and, in the preferred case, an alkali or alkaline earth component.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon dehydrogenation process, andit is intended to include within the scope of the present inventioncarrier materials which have traditionally been utilized indual-function hydrocarbon conversion catalysts such as: (1) activatedcarbon, coke, or charcoal; (2) silica or silica gel, silicon carbide,clays, and silicates including those synthetically prepared andnaturally occurring, which may or may not be acid treated, for example,attapulgus clay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide,cesium oxide, hafnium oxide, zinc oxide, magnesia, boria, thoria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline Zeolitic aluminoslicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, CaAl₂ O₄, and other like compounds havng the formulaMO-Al₂ O₃ where M is a metal having a valence of 2; and (7) combinationsof elements from one or more of these groups. The preferred porouscarrier materials for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas gamma-, eta-, and theta-alumina, with gamma- or eta-alumina givingbest results. In addition, in some embodiments the alumina carriermaterial may contain minor proportions of other well-known refractoryinorganic oxides such as silica, zirconia, magnesia, etc.; however, thepreferred support is substantially pure gamma-or eta-alumina. Preferredcarrier materials have an apparent bulk density of about 0.2 to about0.8 g/cc and surface area characteristics such that the average porediameter is about 20 to 300 Angstroms (B.E.T.), the pore volume is about0.1 to about 1 cc/g (B.E.T.) and the surface area is about 100 to about500 m² /g (B.E.T.). In general, best results are typically obtained witha substantially halogen-free gamma-alumina carrier material which isused in the form of spherical particles having a relatively smalldiameter (i.e. typicaly about 1/16 inch), an apparent bulk density ofabout 0.2 to about 0.8 g/cc, a pore volume of about 0.3 to about 0.8cc/g (B.E.T.), and a surface area of about 125 to about 250 m² /g(B.E.T.).

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or naturally occurring.Whatever type of alumina is employed, it may be activated prior to useby one or more treatments including drying, calcination, steaming, etc.,and it may be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere, and alumina spheres may becontinously manufactured by the well-known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. It is a good practice to subject the calcinedparticles to a high temperature treatment with steam in order to remoeundesired acidic components such as residual chlorine and therey preparethe preferred substantially halogen-free carrier material. Thispreparation procedure effects conversion of the alumina hydrogel to thecorresponding crystalline gamma-alumina. See the teachings of U.S. Pat.No. 2,620,314 for additional details.

Another particularly preferred alumina carrier material is synthesizedfrom a unique crystalline alumina powder which has been characterized inU.S. Pat. Nos. 3,852,190 and 4,012,313 as a by-product from a Zieglerhigher alochol synthesis reaction as described in Zeigler's U.S. Pat.No. 2,892,858. For purposes of simplification, the name "Ziegleralumina" is used herein to identify this material. It is presentlyavailable from the Conoco Chemical Division of Continental Oil Companyunder the trademark Catapal. This material is an extremely high purityalpha-alumina monohydrate (boehmite) which after calcination at a hightemperature has been shown to yield a high purity gamma-alumina. It iscommercially available in three forms: (1) Catapal SB--a spray driedpowder having a typical surface area of 250 m² /g; (2) Catapal NG--arotary kiln dried alumina having a typical surface area of 180 m² /g;and (3) Dispal M--a finely divided dispersable product having a typicalsurface area of about 185 m² /g. For purposes of the present invention,the preferred starting material is the spray dried powder, Catapal SB.This alpha-alumina monohydrate powder may be formed into a suitablecatalyst material according to any of the techniques known to thoseskilled in the catalyst carrier material forming art. Spherical carriermaterial particles can be formed, for example, from this Ziegler aluminaby: (1) converting the alpha-alumina monohydrate powder into an aluminasol by reaction with a suitable peptizing acid and water and thereafterdropping a mixture of the resulting sol and a gelling agent into an oilbath to form spherical particles of an alumina gel which are easilyconverted to a gamma-alumina carrier material by known methods; (2)forming an extrudate from the powder by established methods andthereafter rolling the extrudate particles on a spinning disc untilspherical particles are formed which can then be dried and calcined toform the desired particles of spherical carrier material; and (3)wetting the powder with a suitable peptizing agent and thereafterrolling particles of the powder into spherical masses of the desiredsize in much the same way that children have been known to make parts ofsnowmen by rolling snowballs down hills covered with wet snow. Thealumina powder can also be formed in any other desired shape or type ofcarrier material known to those skilled in the art such as rods, pills,pellets, tablets, granules, extrudates and the like forms by methodswell-known to the practitioners of the catalyst carrier material formingart. The preferred type of carrier material for the present invention isa cylindrical extradate having a diameter of about 1/32"to about 1/8"(especially about 1/16") and a length to diameter (L/D) ratio of about1:1 to about 5:1, with a L/D ratio of about 2:1 being especiallypreferred. The especially preferred extrudate form of the carriermaterial is preferably prepared by mixing the alumina powder with waterand a suitable peptizing agent such as nitric acid, acetic acid,aluminum nitrate and the like material until an extrudable dough isformed. The amount of water added to form the dough is typicallysufficient to give a loss on ignition (LOI) at 500° C. of about 45 to 65wt. %, with a value of about 55 wt. % being especialy preferred. On theother hand, the acid addition rate is generally sufficient to provideabout 2 to 7 wt. % of the volatile free alumina powder used in the mix,with a value of about 3 to 4% being especially preferred. The resultingdough is then extruded thrugh a suitably sized die to form extrudateparticles. It is to be noted that it is within the scope of the presentinvention to treat the resulting dough with an aqueous alkaline reagentsuch as an aqueous solution of ammonium hydroxide in accordance with theteachings of U.S. Pat. No. 3,661,805. This treatment may be performedeither before or after extrusion, with the former being preferred. Theseparticles are then dried at a temperature of about 500° to 800° F. for aperiod of about 0.1 about 5 hours and thereafter calcined at atemperature of about 900° F. to about 1500° F. for a period of about 0.5to about 5 hours to form the preferred extrudate particls of the Ziegleralumina carrier material. In addition, in some embodiments of thepresent invention the Ziegler alumina carrier material may contain minorproportions of other well-known refractory inorganic oxides such assilica, titanium dioxide, zirconium dioxide, chromium oxide, berylliumoxide, vanadium oxide, cesium oxide, hafnium oxide, zinc oxide, ironoxide, cobalt oxide, magnesia, boria, thoria, and the like materialswhich can be blended into the extrudable dough prior to the extrusion ofsame. In the same manner crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with a multivalent cation, such as a rare earth, can beincorporated into this carrier material by blending finely dividedparticles of same into the extrudable dough prior to extrusion of same.A preferred carrier material of this type is a substantiallyhalogen-free and substantially pure Ziegler alumina having an apparentbulk density (ABD) of about 0.4 to 1 g/cc (especially an ABD of about0.5 to about 0.85 g/cc), a surface area (B.E.T.) of about 150 to about280 m² /g (preferably about 185 to about 235 m² /g) and a pore volume(B.E.T.) of about 0.3 to about 0.8 cc/g.

A second essential ingredient of the present activated and attenuatedcatalytic composite is a special ruthenium component which I have chosento characterize as a pyrolyzed ruthenium carbonyl in order to emphasizethat the ruthenium moiety of interest in my invention is the rutheniumproduced by decomposing a ruthenium carbonyl in the presence of a finelydivided dispersion of a platinum group metal and in the absence ofmaterials such as oxygen or water which could interfere with the basicdesired interaction of the ruthenium carbonyl component with theplatinum group metal component as previously explained. In view of thefact that all of the ruthenium contained in a ruthenium carbonylcompound is present in the elemental metallic state, a preferredrequirement of my invention is that the resulting reaction product ofthe ruthenium carbonyl compound or complex with the platinum groupmetal-and rhenium-loaded carrier material is not subjected to conditionswhich could in any way interfere with the maintenance of the rutheniummoiety in the elemental metallic state; consequently, avoidance of anyconditions which would tend to cause the oxidation of any portion of theruthenium ingredient or of the platinum group ingredient is arequirement for full realization of the synergistic interaction enabledby the present invention. This ruthenium carbonyl component may beutilized in the resulting composite in any amount that is catalyticallyeffective with the preferred amount typically corresponding to about0.01 to about 2 wt. % thereof, calculated on an elemental rutheniumbasis. Best results are ordinarily obtained with about 0.05 to about 1wt. % ruthenium. Best results are also achieved when the amount of theruthenium carbonyl component is set as a function of the amount of theplatinum group component to achieve a carbonyl-derived ruthenium toplatinum group metal atomic ratio of about 0.1:1 to about 5:1, with anespecially useful range comprising about 0.2:1 to about 3:1 and withsuperior results achieved at an atomic ratio of ruthenium to platinumgroup metal of about 0.5:1 to about 1.0:1.

The ruthenium carbonyl ingredient may be reacted with the reducedplatinum group metal-and ruthenium-containing porous carrier material inany suitable manner known to those skilled in the catalyst formulationart which results in relatively good contact between the rutheniumcarbonyl complex and the platinum group component contained in theporous carrier material. One acceptable procedure for incorporating theruthenium carbonyl component into the composite involves sublimatingthis complex under conditions which enable it to pass into the vaporphase without being decomposed and thereafter contacting the resultingruthenium carbonyl sublimate with the platinum group metal- andrhenium-containing porous carrier material under conditions designed toachieve intimate contact of the carbonyl reagent with the platinum groupmetal dispersed on the carrier material. Typically, this procedure isperformed under vacuum at a temperature of about 70° to about 250° F.for a period of time sufficient to react the desired amount of rutheniumcarbonyl with the carrier material. In some cases an inert carrier gassuch as nitrogen can be admixed with the ruthenium carbonyl sublimate inorder to facilitate the intimate contacting of same with themetal-containing porous carrier material. A particularly preferred wayof accomplishing this reaction step is an impregnation procedure whereinmetal-containing porous carrier material is impregnated with a suitablesolution containing the desired quantity of the ruthenium carbonylcomplex. For purposes of the present invention, organic solutions arepreferred, although any suitable solution may be utilized as long as itdoes not interact with the ruthenium carbonyl and cause decomposition ofsame. Obviously the organic solution should be anhydrous in order toavoid detrimental interaction of water with the ruthenium carbonylcomplex. Suitable solvents are any of the commonly available organicsolvents such as one of the available ethers, alcohols, ketones,aldehydes, paraffins, naphthenes and aromatic hydrocarbons, for example,acetone, acetyl acetone, benzaldehyde, pentane, hexane, carbontetrachloride, methyl isopropyl ketone, benzene, n-butylether, diethylether, ethylene glycol, methyl isobutyl ketone, diisobutyl ketone andthe like organic solvents. Best results are ordinarily obtained when thesolvent is acetone; consequently, the preferred impregnation solution isruthenium carbonyl dissolved in anhydrous acetone. The rutheniumcarbonyl complex suitable for use in the present invention may be eitherthe pure ruthenium carbonyl itself (i.e. Ru(CO)₅ or Ru₃ (CO)₁₂) or asubstituted ruthenium carbonyl such as the ruthenium carbonyl halidesincluding the chlorides, bromides, and iodides and the like substitutedcarbonyl complexes. After impregnation of the carrier material with theruthenium carbonyl component, it is important that the solvent beremoved or evaporated from the catalyst prior to decomposition of theruthenium carbonyl component by means of the hereinafter describedpyrolysis step. The reason for removal of the solvent is that I believethat the presence of organic materials such as hydrocarbons orderivatives of hydrocarbons during the pyrolysis step is highlydetrimental to the synergistic interaction associated with the presentinvention. This solvent is removed by subjecting the ruthenium carbonylimpregnated carrier material to a temperature of about 100° F. to about250° F. in the presence of an inert gas or under a vacuum conditionuntil no further substantial amount of solvent is observed to come offthe impregnated material. In the preferred case where acetone is used asthe impregnation solvent, this drying of the impregnated carriermaterial typically takes about one half hour at a temperature of about225° F. under moderate vacuum conditions.

After the ruthenium carbonyl component is incorporated into theplatinum-and rhenium containing porous carrier material, the resultingcomposite is, pursuant to the present invention, subjected to pyrolysisconditions designed to decompose substantially all of the rutheniumcarbonyl material, without oxidizing either the platinum group componentor the decomposed ruthenium carbonyl component. This step is preferablyconducted in an atmosphere which is substantially inert to the rutheniumcarbonyl such as in a nitrogen or noble gas-containing atmosphere.Preferably this pyrolysis step takes place in the presence of asubstantially pure and dry hydrogen stream. It is of course within thescope of the present invention to conduct the pyrolysis step undervacuum conditions. It is much preferred to conduct this step in thesubstantial absence of free oxygen and substances that could yield freeoxygen under the conditions selected. Likewise it is clear that bestresults are obtained when this step is performed in the total absence ofwater and of hydrocarbons and other organic materials. I have obtainedbest results in pyrolyzing ruthenium carbonyl while using an anhydroushydrogen stream at pyrolysis conditions including a temperature of about300° F. to about 900° F. or more, preferably about 400° F. to about 750°F., a gas hourly space velocity of about 250 to about 1500 hr.⁻¹ for aperiod of about 0.05 to about 5 or more hours until no further evolutionof carbon monoxide is noted. After the ruthenium carbonyl component hasbeen pyrolyzed, it is a much preferred practice to maintain theresulting catalytic composite in an inert environment (i.e., a nitrogenor the like inert gas blanket) until the catalyst is loaded into areaction zone for use in the conversion of hydrocarbons.

A third essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium, or mixtures thereof as afirst component of the superactive catalytic composite. It is anessential feature of the present invention that substantially all ofthis platinum groul component is uniformly dispersed throughout theporous carrier material in the elemental metallic state prior to theincorporation of the ruthenium carbonyl ingredient. Generally, theamount of this component present in the form of catalytic composites issmall and typically will comprise about 0.01 to about 2 wt. % of finalcatalytic composite, calculated on an elemental basis. Excellent resultsare obtained when the catalyst contains about 0.05 to about 1 wt. % ofplatinum, iridium, rhodium or palladium metal. Particularly preferredmixtures of these platinum group metals preferred for use in thecomposite of the present invention are: (1) platinum and iridium and (2)platinum and rhodium.

This platinum group component may be incoporated in the porous carriermaterial in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogelation, ion-exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate,sodium hexachlororhodate (III) sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium,or palladium chloride compound, such as chloroplatinic, chloroiridic, orchloropalladic acid or rhodium trichloride hydrate, is ordinarilypreferred. Nitric acid or the like acid is also generally added to theimpregnation solution in order to further facilitate the uniformdistribution of the metallic components throughout the carrier material.In addition, it is generally preferred to impregnate the carriermaterial after it has been calcined in order to minimize the risk ofwashing away the valuable platinum group component.

A fourth essential constituent of the multimetallic catalyst of thepresent invention is a rhenium component. This component may in generalbe present in the instant catalytic composite in any catalyticallyavailable form such as the elemental metal, a compound like the oxide,hydroxide, halide, oxyhalide, sulfide, or in chemical combination withone or more of the other ingredients of the catalyst. Although it is notintended to restrict the present invention by this explanation, it isbelieved that best results are obtained when the rhenium component ispresent in the composite in a form wherein substantially all of therhenium moiety is in the elemental metallic state or in a state which isreducible to the elemental metallic state under hydrocarbon conversionconditions or in a mixture of these states. This rhenium component canbe used in any amount which is catalytically effective, with goodresults obtained, on an elemental basis, with about 0.01 to about 5 wt.% rhenium in the catalyst. Best results are ordinarily achieved withabout 0.05 to about 1 wt. % rhenium, calculated on an elemental basisand with an atomic ratio of rhenium to platinum group metal of about0.1:1 to about 10:1, especially about 0.5:1 to about 5:1.

This rhenium component may be incorporated into the porous carriermaterial in any suitable manner known to the art to result in arelatively uniform dispersion of the rhenium moiety in the carriermaterial, such as by coprecipitation or cogelation or coextrusion withthe porous carrier material, ion exchange with the gelled carriermaterial, or impregnation of the carrier material either after, before,or during the period when it is dried and calcined. It is to be notedthat it is intended to include within the scope of the present inventionall conventional methods for incorporating and simultaneously uniformlydistributing a metallic component in a catalytic composite and theparticular method of incorporation used is not deemed to be an essentialfeature of the present invention. One acceptable method of incorporatingthe rhenium component into the porous carrier material involvescogelling or coprecipitating the rhenium component in the form of thecorresponding hydrous oxide during the preparation of the preferredcarrier material, alumina. This method typically involves the additionof a suitable sol-soluble and decomposable rhenium compound such asperrhenic acid or a salt thereof to the alumina hydrosol and thencombining the hydrosol with a suitable gelling agent and dropping theresulting mixture into an oil bath, etc., as explained in detailhereinbefore. After drying and calcining the resulting gelled carriermaterial in air, there is obtained an intimate combination of aluminaand rhenium oxide and/or oxychloride. An especially preferred method ofincorporating the rhenium component into the porous carrier materialinvolves utilization of a soluble, decomposable compound of rhenium toimpregnate the porous carrier material. In general, the solvent used inthis impregnation step is selected on the basis of the capability todissolve the desired rhenium compound without adversely affecting thecarrier material or the other ingredients of the catalyst--for example,a suitable alcohol, ether, acid and the like solvents. The solvent ispreferably an aqueous, acidic solution. The rhenium component may beadded to the carrier material by commingling the latter with an aqueousacidic solution of suitable rhenium salt, complex, or compound such asperrhenic acid, ammonium perrhenate, sodium perrhenate, potassiumperrhenate, potassium rhenium oxychloride (K₂ ReOCl₅), potassiumhexachlororhenate (IV), rhenium chloride, rhenium heptoxide and the likecompounds. A particularly preferred impregnation solution comprises anacidic aqueous solution of perrhenic acid. Suitable acids for use in theimpregnation solution are: inorganic acids such as hydrochloric acid,nitric acid, and the like, and strongly acidic organic acids such asoxalic acid, malonic acid, citric acid, and the like. In general, therhenium component can be impregnated either prior to, simultaneouslywith, or after the platinum group component is added to the carriermaterial. However, excellent results are obtained when the rhenimcomponent is added simultaneously with the addition of the platinumgroup component.

A highly preferred optional ingredient of the catalyst used in thepresent invention is an alkali or alkaline earth component. Morespecifically, this component is selected from the group consisting ofthe compounds of the alkali metals--cesium, rubidium, potassium, sodium,and lithium--and of the alkaline earth metals--calcium, strontium,barium, and magnesium. This component exists within the catalyticcomposite in an oxidation state above that of the elemental metal as arelatively stable compound such as the oxide or hydroxide, or incombination with one or more of the other components of the composite,or in combination with the carrier material such as, for example, in theform of an alkali or alkaline earth metal aluminate. Since, as isexplained hereinafter, the composite containing the alkali or alkalineearth component is always calcined or oxidized in an air atmospherebefore use in the dehydrogenation of hydrocarbons, the most likely statethis component exists in during use in the dehydrogenation reaction isthe corresponding metallic oxide such as lithium oxide, potassium oxide,sodium oxide, and the like. Regardless of what precise form in which itexists in the composite, the amount of this component utilized ispreferably selected to provide a nonacidic composite containing about0.1 to about 5 wt. % of the alkali metal or alkaline earth metal, and,more preferably, about 0.25 to about 3.5 wt. %. Best results areobtained when this component is a compound of lithium or potassium. Thefunction of this component is to neutralize any of the acidic materialsuch as halogen which may have been used in the preparation of thepresent catalyst so that the final catalyst is nonacidic.

The alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art toresult in a relatively uniform dispersion of this component throughoutthe carrier material with consequential neutralization of any acidicsites which may be present therein. Typically good results are obtainedwhen it is combined by immpregnation, coprecipitation, ion-exchange, andthe like procedures. The preferred procedure, however, involvesimpregnation of the carrier material either before, during or after itis calcined, or berfore, during or after the other metallic ingredientsare added to the carrier material. Best results are ordinarily obtainedwhen this component is added to the carrier material simultaneously withor after the platinum group component and rhenium component, and beforethe ruthenium carbonyl component because the alkali metal or alkalineearth metal component acts to neutralize the acidic materials used inthe preferred impregnation procedure for the platinum group and rheniumcomponents. In fact, it is preferred to add the platinum group, rheniumand alkali or alkaline earth components to the carrier material, oxidizethe resulting composite in a wet air stream at a high temperature (i.e.typically about 600° to 1000° F.), then treat the resulting oxidizedcomposite with steam or a mixture of air and steam at a relatively hightemperature of about 600° to about 1050° F. in order to remove at leasta portion of any residual acidity and thereafter add the rutheniumcarbonyl component. Typically, the impregnation of the carrier materialwith this component is performed by contacting the carrier material witha solution of a suitable decomposable compound or salt of the desiredalkali or alkaline earth metal. Hence, suitable compounds include thealkali or alkaline earth metal halides, nitrates, acetates, carbonates,phosphates, and the like compounds. For example, excellent results areobtained by impregnating the carrier material with an aqueous solutionof chloroplatinic acid, perrhenic acid, lithium nitrate or potassiumnitrate and nitric acid. Ordinarily, the amount of alkali or alkalineearth component is selected to produce a composite having an atomicratio of alkali metal or alkaline earth metal to platinum group metal ofabout 5:1 to about 100:1 or more, with the preferred range being about10:1 to about 75:1.

After the platinum group component, rhenium component and optionalalkali or alkaline earth component are combined with the porous carriermaterial, the resulting metals-containing carrier material willgenerally be dried at a temperature of about 200° F. to about 600° F.for a period of typically about 1 to about 24 hours or more andthereafter oxidized at a temperature of about 600° F. to about 1100° F.in an air or oxygen atmosphere for a period of about 0.5 to about 10 ormore hours effective to convert substantially all of the platinum group,rhenium and alkali or alkaline earth components to the correspondingoxide forms. When acidic materials are used in incorporating thesemetallic components, best results are ordinarily achieved when theresulting oxidized composite is subjected to a high temperaturetreatment with steam or with a mixture of steam and a diluent gas suchas air or nitrogen either during or after this oxidation step in orderto remove as much as possible of the undesired acidic components such ashalogen and thereby prepare a substantially halogen-free,metals-containing oxidized carrier material. It is to be noted that itis essential that conditions used in this acidic component strippingstep be very carefully chosen to avoid any possibility of sintering oragglomerating the platinum group component.

A preferred feature of the present invention involves subjecting theresulting oxidized, platinum group metal- and rhenium-containing, andtypically alkali or alkaline earth metal-containing carrier material toa substantially water-free reduction step before the incorporation ofthe ruthenium component by means of the ruthenium carbonyl reagent. Theimportance of this reduction step comes from my observation that when anattempt is made to prepare the instant catalytic composite without firstreducing the platinum group component, no significant improvement in theplatinum-ruthenium-rhenium catalyst system is obtained; put another way,it is my finding that it is essential for the platinum group componentto be well dispersed in the porous carrier material in the elementalmetallic state prior to incorporation of the ruthenium component by theunique procedure of the present invention in order for synergisticinteraction of the ruthenium carbonyl with the dispersed platinum groupmetal to occur according to the theories that I have previouslyexplained in my prior application Ser. No. 246,828. Accordingly, thisreduction step is designed to reduce substantially all of the platinumgroup component to the elemental metallic state and to assure arelatively uniform and finely divided dispersion of this metalliccomponent throughout the porous carrier material. Preferably, asubstantially pure and dry hydrogen-containing stream (by use of theword "dry" I mean that it contains less than 20 vol. ppm water andpreferably less than 5 vol. ppm water) is used as the reducing agent inthis step. The reducing agent is contacted with the oxidized, platinumgroup metal- and rhenium containing carrier material at conditionsincluding a reduction temperature of about 450° F. to about 1200° F. fora period of about 0.5 to about 10 or more hours selected to reducesubstantially all of the platinum group component to the elementalmetallic state. Once this condition of finely divided dispersed platinumgroup metal in the porous carrier material is achieved, it is importantthat environments and/or conditions that could disturb or change thiscondition be avoided; specifically, I much prefer to maintain thefreshly reduced carrier material containing the platinum group metalunder a blanket of inert gas to avoid any possibility of contaminationof same either by water or by oxygen. After this step, the specialruthenium component is composited with the reduced platinum groupmetal-rhenium containing carrier in the manner disclosed above.

The resulting pyrolyzed catalytic composite may, in some cases, bebeneficially subjected to a presulfiding step designed to incorporate inthe catalytic composite from about 0.01 to about 1 wt. % sulfurcalculated on an elemental basis. Preferably, this presulfidingtreatment takes place in the presence of hydrogen and a suitabledecomposable sulfur-containing compound such as hydrogen sulfide, lowermolecular weight mercaptans, organic sulfides, etc. Typically, thisprocedure comprises treating the pyrolyzed catalyst with a sulfiding gassuch as a mixture of hydrogen and hydrogen sulfide containing 1 to about10 moles of hydrogen per mole of hydrogen sulfide at conditionssufficient to effect the desired incorporation of sulfur, generallyincluding a temperature ranging from about 50° F. to about 1000° F. Itis generally a preferred practice to perform this presulfiding stepunder substantially water-free and oxygen-free conditions. It is withinthe scope of the present invention to maintain or achieve the sulfidedstate of the present catalyst during use in the dehydrogenation ofhydrocarbons by continuously or periodically adding a decomposablesulfur-containing compound, selected from the above-mentioned list, tothe reactor containing the super-active catalyst in an amount sufficientto provide about 1 to 500 wt. ppm, preferably about 1 to about 20 wt.ppm of sulfur, based on hydrocarbon charge. According to another mode ofoperation, this sulfiding step may be accomplished during the pyrolysisstep by utilizing a ruthenium carbonyl reagent which has asulfur-containing ligand or by adding H₂ S to the hydrogen stream whichis preferably used therein.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with the multimetallic catalytic compositedescribed above in a dehydrogenation zone maintained at dehydrogenationconditions. This contacting may be accomplished by using the catalyst ina fixed bed system, a moving bed system, a fluidized bed system, or in abatch type operation; however, in view of the danger of attrition lossesof the valuable catalyst and of well-known operational advantages, it ispreferred to use a fixed bed system. In this system, the hydrocarbon offeed stream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrogenation zonecontaining a fixed bed of the catalyst previously characterized. It is,of course, understood that the dehydrogenation zone may be one or moreseparate reactors with suitable heating means therebetween to insurethat the desired conversion temperature is maintained at the entrance toeach reactor. It is also to be noted that the reactants may be contactedwith the catalyst bed in either upward, downward, or radial flow fashionwith the latter being preferred. In addition, it is to be noted that thereactants may be in the liquid phase, a mixed liquid-vapor phase, or avapor phase when they contact the catalyst, with best results obtainedin the vapor phase.

Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized, either individually or in admixture withhydrogen or each other, such as steam, methane, ethane, carbon dioxide,and the like diluents. Hydrogen is preferred because it serves thedual-function of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite.Ordinarily, hydrogen is utilized in amounts sufficient to insure ahydrogen to hydrocarbon mole ratio of about 1:1 to about 20:1, with bestresults obtained in the range of about 1.5:1 to about 10:1. The hydrogensteam charged to the dehydrogenation zone will typically be recycledhydrogen obtained from the effluent stream from this zone after asuitable hydrogen separation step. As explained in my prior applicationSer. No. 246,828, a highly preferred mode of operation of the instantdehydrogenation method is in a substantially water-free environment;however, when utilizing hydrogen in the instant method, improvedselectivity results are obtained under certain limited circumstances ifwater or a water-producing substance (such as an alcohol), ketone,ether, aldehyde, or the like oxygen-containing decomposable organiccompound) is added to the dehydrogenation zone in an amount calculatedon the basis of equivalent water, corresponding to about 1 to about5,000 wt. ppm. of the hydrocarbon charge stock, with about 1 to 1,000wt. ppm. of water giving best results. This water addition feature maybe used on a continuous or intermittent basis to regulate the activityand selectivity of the instant catalyst.

Regarding the conditions utilized in the method of the presentinvention, these are generally selected from the dehydrogenationconditions well-known to those skilled in the art for the particulardehydrogenatable hydrocarbon which is charged to the process. Morespecifically, suitable conversion temperatures are selected from therange of about 700° to about 1300° F. with a value being selected fromthe lower portion of this range for the more easily dehydrogenatedhydrocarbons such as the long chain normal paraffins and from the higherportion of this range for the more difficultly dehydrogenatedhydrocarbons such as propane, butane, and the like hydrocarbons. Forexample, for the dehydrogenation of C₆ to C₃₀ normal paraffins, bestresults are ordinarily obtained at a temperature of about 800° to about950° F.; on the other hand, for the dehydrogenation of propane, bestresults are usually achieved at a temperature of about 1150° F. to 1250°F. The pressure utilized is ordinarily selected at a value which is aslow as possible consistent with the maintenance of catalyst stabilityand is usually about 0.1 to about 10 atmospheres with best resultsordinarily obtained in the range of about 0.5 to about 3 atmospheres. Inaddition, a liquid hourly space velocity (calculated on the basis of thevolume amount, as a liquid, of hydrocarbon charged to thedehydrogenation zone per hour divided by the volume of the catalyst bedutilized) is selected from the range of about 1 to about 40 hr.⁻¹, withbest results for the dehydrogenation of long-chain normal paraffinstypically obtained at a relatively high space velocity of about 20 to 35hr.⁻¹ and for the more refractory paraffins at a space velocity of about3 to about 10 hr.⁻¹.

Regardless of the details concerning the operations of thedehydrogenation step, an effluent stream will be withdrawn therefrom.This effluent will usually contain unconverted dehydrogenatablehydrocarbons, hydrogen, and products of the dehydrogenation reaction.This stream is typically cooled and passed to a hydrogen-separating zonewherein a hydrogen-rich vapor phase is allowed to separate from thehydrocarbon-rich liquid phase. In general, it is usually desired torecover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery operation can beaccomplished in any suitable manner known to the art such as by passingthe hydrocarbon-rich liquid phase through a bed of suitable absorbentmaterial which has the capability to selectively retain thedehydrogenated hydrocarbons contained therein or by contacting same witha solvent having a high selectivity for the dehydrogenated hydrocarbon,or by a suitable fractionation scheme where feasible. In the case wherethe dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbentshaving this capability are activated silica gel, activated carbon,activated alumina, various types of specially prepared zeoliticcrystalline aluminosilicates, molecular sieves, and the like adsorbents.In another typical case, the dehydrogenated hydrocarbons can beseparated from the unconverted dehydrogenatable hydrocarbons byutilizing the inherent capability of the dehydrogenated hydrocarbons toeasily enter into several well-known chemical reactions such asalkylation, oligomerization, halogenation, sulfonation, hydration,oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen-separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycledthrough suitable compressing means to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal paraffin hydrocarbons are dehydrogenated to the correspondingnormal mono-olefins, a preferred mode of operation of this hydrocarbonrecovery step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the hydrogen-separatingzone is combined with a stream containing an alkylatable aromatic andthe resulting mixture passed to an alkylation zone containing a suitablehighly acid catalyst such as an anhydrous solution of hydrogen fluoride.In the alkylation zone the mono-olefins react with alkylatable aromaticwhile the unconverted normal paraffins remain substantially unchanged.The effluent stream from the alkylation zone can then be easilyseparated, typically by means of a suitable fractionation system, toallow recovery of the unreacted normal paraffins. The resulting streamof unconverted normal paraffins is then usually recycled to thedehydrogenation step of the present invention.

The following illustrative embodiments are introduced to describefurther the dehydrogenation method and the multimetallic catalyticcomposite of the present invention. These examples of specificembodiments of the present invention are intended to be illustrativerather than restrictive.

These examples are all to be performed in a laboratory scaledehydrogenation plant comprising a reactor, a hydrogen separating zone,heating means, cooling means, pumping means, compressing means, and thelike conventional equipment. In this plant, the feed stream containingthe dehydrogenatable hydrocarbon is combined with a hydrogen-containing,substantially water-free, recycle gas stream and the resulting mixtureheated to the desired conversion temperature, which refers herein to thetemperature maintained at the inlet to the reactor. The heated mixtureis then passed into contact with the instant multimetallic catalystwhich is maintained as a fixed bed of catalyst particles in the reactor.The pressures reported herein are recorded at the outlet from thereactor. An effluenct stream is withdrawn from the reactor, cooled, andpassed into the hydrogen-separating zone wherein a hydrogen-containinggas phase separates from a hydrogen-rich liquid phase containingdehydrogenated hydrocarbons, unconverted dehydrogenatable hydrocarbons,and a minor amount of side products of the dehydrogenation reaction. Aportion of the hydrogen-containing gas phase is recovered as excessrecycle gas with the remaining portion being continuously recycled,after water addition as needed, through suitable compressing means tothe heating zone as described above. The hydrocarbon-rich liquid phasefrom the separating zone is withdrawn therefrom and subjected toanalysis to determine conversion and selectivity for the desireddehydrogenated hydrocarbon as will be indicated in the Examples.Conversion numbers of the dehydrogenatable hydrocarbon reported hereinare all calculated on the basis of disappearance of the dehydrogenatablehydrocarbon and are expressed in mole percent. Similarly, selectivitynumbers are reported on the basis of moles of desired hydrocarbonproduced per 100 moles of dehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are to be preparedaccording to the following preferred method with suitable modificationin stoichiometry to achieve the compositions reported in each example.First an alumina carrier material comprising 1/16 inch spheres having anapparent bulk density of about 0.3 g/cc is prepared by: forming analuminum hydroxy chloride sol by dissolving substantially pure aluminumpellets in a hydrochloric acid solution, adding hexamethylenetetramineto the resulting alumina sol, gelling the resulting solution by droppingit into an oil bath to form spherical particles of an alumina hydrogel,aging, and washing the resulting particles with an ammonical solutionand finally drying, calcining, and steaming the aged and washedparticles to form spherical particles of a substantially halogen-freegamma-alumina containing substantially less than 0.1 wt. % combinedchloride. Additional details as to this method of preparing this aluminacarrier material are given in the teachings of U.S. Pat. No. 2,620,314.

An aqueous impregnation solution containing chloroplatinic acid,perrhenic acid, nitric acid and (when an alkali or alkaline earthcomponent is used) either lithium nitrate or potassium nitrate is thenprepared. The alumina carrier material is thereafter admixed with theimpregnation solution. The amounts of the metallic reagents contained inthis impregnation solution are calculated to result in a final compositecontaining the hereafter specified amounts of the metallic components.In order to insure uniform dispersion of the platinum componentthroughout the carrier material, the amount of nitric acid used in thisimpregnation solution is about 5 wt. % of the alumina particles. Thisimpregnation step is performed by adding the carrier material particlesto the impregnation mixture with constant agitation. In addition, thevolume of the solution is approximately the same as the bulk volume ofthe alumina carrier material particles so that all of the particles areimmersed in the impregnation solution. The impregnation mixture ismaintained in contact with the carrier material particles for a periodof about 1/2 to about 3 hours at a temperature of about 70° F.Thereafter, the temperature of the impregnation mixture is raised toabout 225° F. and the excess solution is evaporated in a period of about1 hour. The resulting dried impregnated particles are then subjected toan oxidation treatment in a dry air stream at a temperature of about975° F. and a GHSV of about 500 hr.⁻¹ for about 1/2 hour. This oxidationstep is designed to convert substantially all of the metallicingredients to the corresponding oxide forms. The resulting oxidizedspheres are subsequently contacted in a steam stripping step with an airstream containing about 1 to about 30% steam at a temperature of about800° to about 1000° F. for an additional period of about 1 to about 5hours in order to reduce any residual combined chloride to a value lessthan 0.5 wt. % and most preferably less than 0.2 wt. %. The oxidized andsteam-stripped spheres are thereafter subjected to a second oxidationstep with a dry air stream at 975° F. and a GHSV of 500 hr.⁻¹ for anadditional period of about 1/2 hour.

The resulting oxidized, steam-stripped carrier material particles arethen subjected to a dry reduction treatment designed to reducesubstantially all of the platinum component to the elemental state andto maintain a uniform dispersion of this component in the carriermaterial. This reduction step is accomplished by contacting theparticles with a hydrocarbon-free, dry hydrogen stream containing lessthan 5 vol. ppm H₂ O at a temperature of about 1050° F., a pressureslightly above atmospheric, a flow rate of hydrogen through theparticles corresponding to a GHSV of about 400 hr.⁻¹ and for a period ofabout one hour.

Ruthenium carbonyl complex, Ru₃ (CO)₁₂, is thereafter dissolved in ananhydrous acetone solvent in order to prepare the ruthenium carbonylsolution which is used as the vehicle for reacting ruthenium carbonylwith the carrier material containing the uniformly dispersed platinumand rhenium. The amount of this complex used is selected to result in afinished catalyst containing about 0.1 wt. % ruthenium derived fromruthenium carbonyl. The resulting ruthenium carbonyl-containing solutionis then contacted under appropriate impregnation conditions with thereduced platinum- and rhenium-containing alumina carrier materialresulting from the previously described reduction step. The impregnationconditions utilized are: a contact time of about one half to about threehours, a temperature of about 70° F. and a pressure of aboutatmospheric. It is important to note that this impregnation step isconducted under a nitrogen blanket so that oxygen was excluded from theenvironment and also this step is performed under anhydrous conditions.Therefore the acetone solvent is removed under flowing nitrogen at atemperature of about 175° F. for a period of about one hour. Theresulting dry ruthenium carbonly impregnated particles are thensubjected to a pyrolysis step designed to decompose the rutheniumcarbonyl components. This step involves subjecting the rutheniumcarbonyl impregnated particles to a flowing hydrogen stream at a firsttemperature of about 230° F. for about one half hour at a GHSV of about600 hr.⁻¹ and at atmospheric pressure. Thereafter in the second portionof the pyrolysis step the temperature of the impregnated particles israised to about 575° F. for an additional interval of about one houruntil the evolution of CO was no longer evident.

The resulting pyrolyzed catalytic composite is then maintained under anitrogen blanket and cooled to a temperature of about 70° F. Thesecatalyst particles are then loaded under a nitrogen blanket into a mildagitation device designed to slowly roll the catalyst particles so as toprovide good contact between these particles and their gaseousenvironment. The agitation device is fitted with an inlet means designedto allow fixed quantities of H₂ S to be periodically injected into thegaseous environment contained therein. Initially this gaseousenvironment is of course pure nitrogen. The amount of H₂ S necessary tosulfide the catalyst to a level of about 600 wt. ppm is then calculated.The necessary amount of H₂ S is then divided into five portions whichare then separately added via the inlet means to the agitation device at15 minute intervals. The conditions utilized during this sulfiding stepare: a temperature of about 70° F., a pressure of about atmospheric anda contact time of sulfiding agent with the catalyst particles of about 1and 1/4 hours. The resulting sulfided catalyst is then maintained undera nitrogen blanket until it is loaded into the reactor in thesubsequently described dehydrogenation tests.

EXAMPLE 1

The reactor is loaded with 100 cc of a catalyst containing, on anelemental basis, 0.1 wt. % ruthenium, 0.375 wt. % platinum, 0.25 wt. %rhenium, and less than 0.15 wt. % chloride. This corresponds to anatomic ratio of ruthenium to platinum of 0.5:1 and of rhenium toplatinum of 0.7:1. The feed stream utilized is commercial gradeisobutane containing 99.7 wt. % of isobutane and 0.3 wt. % normalbutane. The feed stream is contacted with the catalyst at a temperatureof 975° F., a pressure of 10 psig, a liquid hourly space velocity of 4.0hr.⁻¹, and a hydrogen gas to hydrocarbon mole ratio of 3:1. Thedehydrogenation plant is lined-out at these conditions and a 20-hourtest period commenced. The hydrocarbon product stream from the plant iscontinuously analyzed by GLC (gas liquid chromatography) and a highconversion of isobutane is observed with a high selectivity forisobutylene.

EXAMPLE II

The catalyst contains, on an elemental basis, 0.1 wt. % ruthenium, 0.375wt. % platinum, 0.25 wt. % rhenium, 1.0 wt. % lithium, and less than0.15 wt. % combined chloride. These amounts correspond to the followingatomic ratios: Ru/Pt of 0.5:1, Re/Pt of 0.7:1, and Li/Pt of 75:1. Thefeed stream is commercial grade normal dodecane. The hydrogenationreactor is operated at a temperature of 850° F., a pressure of 10 psig,a liquid hourly space velocity of 32 hr.⁻¹, and a hydrogen gas tohydrocarbon mole ratio of 5:1. After a line-out period, a 20-hour testperiod is performed during which the average conversion of the normaldodecane is maintained at a high level with a selectivity for normaldodecene of about 90%.

EXAMPLE III

The catalyst is the same as utilized in Example II. The feed stream isnormal tetradecane. The conditions utilized are a temperature of 830°F., a pressure of 20 psig, a liquid hourly space velocity of 32 hr.⁻¹,and a hydrogen gas to hydrocarbon mole ratio of 4:1. After a line-outperiod, a 20-hour test shows an average conversion of about 12%, and aselectivity for normal tetradecene of about 90%.

EXAMPLE IV

The catalyst contains, on an elemental basis, 0.1 wt. % ruthenium. 0.375wt. % platinum, 0.25 wt. % rhenium, and 0.9 wt. % lithium, with combinedchloride being less than 0.2 wt. %. The pertinent atomic ratios are:Ru/Pt of 0.5:1, Re/Pt of 0.7:1 and Li/Pt of 68:1. The feed stream issubstantially pure cyclohexane. The conditions utilized are atemperature of 900° F., a pressure of 100 psig, a liquid hourly spacevelocity of 3.0 hr.⁻¹, and a hydrogen gas to hydrocarbon mole ratio of4:1. After a line-out period, a 20-hour test is performed with almostcomplete conversion of cyclohexane to benzene and hydrogen.

EXAMPLE V

The catalyst is the same as in Example IV. The feed stream is commercialgrade ethylbenzene. The conditions utilized are a pressure of 15 psig, aliquid hourly space velocity of 32 hr.⁻¹, a temperature of 1010° F., anda hydrogen gas to hydrocarbon mole ratio of 3:1. During a 20-hour testperiod, 85% or more of equilibrium conversion of the ethylbenzene isobserved. The selectivity for styrene is about 90%.

EXAMPLE VI

The catalyst contains, on an elemental basis, about 0.1 wt. % ruthenium,about 0.375 wt. % platinum, about 0.25 wt. % rhenium, about 0.8 wt. %potassium and less than 0.2 wt. % chlorine. The relevant atomic ratiosare: Ru/Pt of 0.5:1, Re/Pt of 0.7:1 and K/Pt of 11:1. The charge stockis substantially pure propane. The conditions utilized are: an inletreaction temperature of 1150° F., a pressure of 10 psig, hydrogen topropane mole ratio of 2:1 and a liquid hourly space velocity of about 5hr.⁻¹. Results are: a conversion of propane of about 35% at aselectivity for propylene of about 85%.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in thecatalyst-formulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:
 1. A method for dehydrogenating adehydrogenatable hydrocarbon comprising contacting the hydrocarbon, athydrocarbon dehydrogenation conditions, with a catalytic compositecomprising a combination of a catalytically effective amount of apyrolyzed ruthenium carbonyl component with a porous carrier materialcontaining a uniform dispersion of a catalytically effective amount of aplatinum group component maintained in the elemental metallic stateduring the incorporation and pyrolysis of the ruthenium carbonylcomponent, and of a rhenium component.
 2. A method as defined in claim 1wherein the dehydrogenatable hydrocarbon is admixed with hydrogen whenit contacts the catalytic composite.
 3. A method as defined in claim 1wherein the platinum group component is platinum.
 4. A method as definedin claim 1 wherein the catalytic composite contains the components inamounts, calculated on an elemental basis, corresponding to about 0.01to about 2 wt. % ruthenium, about 0.01 to about 2 wt. % platinum groupcomponent and about 0.01 to about 5 wt. % rhenium.
 5. A method asdefined in claim 1 wherein the porous carrier material is alumna.
 6. Amethod as defined in claim 1 wherein the catalytic composite is in asubstantially halogen-free state.
 7. A method as defined in claim 1wherein the dehydrogenatable hydrocarbon is an aliphatic hydrocarboncontaining 2 to 30 carbon atoms per molecule.
 8. A method as defined inclaim 1 wherein the dehydrogenatable hydrocarbon is a naphthene.
 9. Amethod as defined in claim 1 wherein the dehydrogenatable hydrocarbon isan alkylaromatic, the alkyl group of which contains about 2 to 6 carbonatoms.
 10. A method for dehydrogenating a dehydrogenatable hydrocarboncomprising contacting the hydrocarbon with a nonacidic catalyticcomposite comprising a combination of a catalytically effective amountof a pyrolyzed ruthenium carbonyl component with a porous carriermaterial containing a uniform dispersion of catalytically effectiveamounts of a platinum group component which is maintained in theelemental metallic state during the incorporation and pyrolysis of theruthenium carbonyl component, a rhenium component, and an alkali oralkaline earth component.
 11. A method as defined in claim 10 whereinthe dehydrogenatable hydrocarbon is admixed with hydrogen when itcontacts the catalytic composite.
 12. A method as claimed in claim 10wherein the dehydrogenatable hydrocarbon is an aliphatic hydrocarboncontaining 2 to 30 carbon atoms per molecule.
 13. A method as defined inclaim 10 wherein the dehydrogenatable hydrocarbon is an alkylaromatic,the alkyl group of which contains about 2 to 6 carbon atoms.
 14. Amethod as defined in claim 10 wherein the dehydrogenatable hydrocarbonis a naphthene.
 15. A method as defined in claim 11 wherein thedehydrogenation conditions include a temperature of about 700 ° to about1200° F., a pressure of about 0.1 to about 10 atmospheres, an LHSV ofabout 1 to about 40 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio ofabout 1:1 to about 20:1.